Evaluation of carcass scraping to enumerate bacteria on pre-chill broiler carcasses

Authors: Smith, Douglas; Cason Jr, John; FLETCHER, D - UGA; HANNAH, J - UGA

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2007
Publication Date: 6/20/2007
Citation: Smith, D.P., Cason Jr, J.A., Fletcher, D.L., Hannah, J.F. 2007. Evaluation of carcass scraping to enumerate bacteria on pre-chill broiler carcasses. Poultry Science. 86:1436-1439.

Interpretive Summary: It is important for poultry processors to know the number and type of bacteria present on chicken carcasses so they can measure and adjust, if necessary, procedures used to lower overall bacterial numbers or eliminate bacteria that cause illness. Traditional methods for determining bacteria, such as rinsing the entire carcass in nearly a pint of fluid may be somewhat expensive and difficult to conduct. Carcass rinsing may also not easily remove bacteria from the surfaces, which would result in artificially lower numbers. A method of scraping a portion of the carcass, then rinsing the scrape blade, was evaluated and compared to the carcass rinsing method. This method has the advantage of being simpler, less expensive, and should recover more bacteria from the surface. Scraping and rinsing the blade, however, produced fewer bacteria than the carcass rinse, even when conversions to account for surface area differences were allowed. In this experiment the scrape method was not as useful as the whole carcass rinse. Also, scraping large areas of carcasses (one entire half) and then rinsing did not produce more bacteria. However, the scrape method is useful for determining if different areas on the same carcass have different numbers of bacteria; the skin on the back of the carcass had more bacteria than the breast skin.

Technical Abstract: Experiments were conducted to evaluate a scraping method for enumerating bacteria on broiler carcasses. In Experiment 1, coliforms and E. coli were determined by the whole carcass rinse method (WCR) and scraping the skin surface and rinsing the blade (BR). In each of two replicate trials, four pre-chill broiler carcasses were collected from two different commercial processing plants. WCR was conducted on each carcass, then a blunt edge blade was used to scrape an area measuring approximately 80 square cm of the breast (front) skin and on the back of the carcass. After scraping, each blade and adhering residue was rinsed in 30 mL 0.1% peptone. One mL of rinsate each from the WCR and BR was plated to determine total coliforms and E. coli. In Experiment 2, six carcasses were collected from a processing plant in each of two replicate trials. Carcasses were split, with one half scraped on all skin surfaces, and the other half remaining unscraped as control; all halves were then subjected to half carcass rinses (HCR) using 200 ml 0.1 % peptone. Coliforms and E. coli were enumerated. Results from both experiments are reported as log cfu/mL. In Experiment 1, mean coliform WCR counts (5.1) were significantly higher (P<0.05) than back BR (2.8), which were higher than front BR (2.2). Mean E. coli WCR counts (4.5) were higher than back BR (2.4), which were higher than front BR (1.6). BR counts adjusted for the greater surface area sampled by WCR were still lower than WCR counts. Experiment 2 results showed no difference between control and scraped carcass halves for coliforms (4.7) or E. coli (4.6). Overall, results show that scraping prior to rinsing does not increase enumeration of coliforms or E. coli. Scraping could be a viable method to compare numbers of bacteria on different areas of the same carcass.